This application claims the priority of Korean Patent Application No. 2002-69419, filed on Nov. 9, 2002, in the Korean Intellectual Property Office, the contents of which are incorporated herein in their entirety by reference.
1. Field of the Invention
The present invention relates to a method and an apparatus for controlling the constant linear velocity of a spindle motor used in an optical system, and more particularly, to a method and apparatus for controlling the constant linear velocity of a spindle motor used in an optical system by comparing the width of a mirror signal or an equivalent of the mirror signal in a first logic state to the width of the mirror signal or equivalent of the mirror signal in a second logic state.
2. Description of the Related Art
Optical systems are apparatuses for recording data on and/or reproducing data from an optical disk, such as a laser-disc (LD), a compact disc (CD), or a digital versatile disc (DVD).
A typical spindle motor, used in an apparatus that reproduces data from an optical disk, rotates an optical disk at a constant linear velocity (CLV). The rotation speed of the optical disk at the inner track is different from the rotation speed at the outer track. In addition, optical disks with different diameters, for example, 8 cm and 12 cm have different mass measurements.
Accordingly, when the servo of an apparatus, which reproduces data from an optical disk, attempts to stop the operation of a spindle motor or the rotation of an optical disk in response to a ‘stop’ command, it is difficult to precisely estimate how much force should be applied to the spindle motor in order to stop it. This is because, as described above, the rotation speed of an optical disk varies depending on whether measuring at an inner track or an outer track. In addition, it is also difficult to determine how long it will take to stop the spindle motor.
If an ‘open’ command is applied and the spindle motor is motionless in response to the ‘stop’ command, the optical disk may deviate from a chuck while rotating and then may skid in the tray, which results in damage to data recorded on the optical disk.
It is difficult to determine the speed of the optical disk because of the fact that the rotation speed of the optical disk varies by up to 1 X depending on the location of the pickup and/or depending on whether measuring the inner track or outer track of the optical disk. Thus, when a ‘reproduce’ command is applied, the spindle motor rotates in response to a CLV kick signal first and then the operation mode of the spindle motor changes to a CLV automatic mode. In this case, the rotation speed of the spindle motor is controlled based on estimation, and accordingly, the operation of the spindle motor is inevitably unstable and imprecise.